Sweep circuit system



July 4, 1950 l.. A.`DE: ROSA ET AL M3293 SWEEP CIRCUIT SYSTEM FiledApril 9, 1945 .SOURCE USC/LATOR ATTORNEY Patented July 4, 1950 Unirsesrnriss referia-nr S-Gla-ims. l

The Ypresent invention nrelates 'to sweep circuit systems for rotatingthe beam of cathode .Tay :tubes and particularly 'to :those 'systems`.where 'signals are used to vradially l"deflect the circular trace thusproduced.

Incertain direction finding systems, aswell as Ain other systems, the'beam-of a cathode rray tube ror oscilloscope is lmoved in acircle=overthe-screen 'at a relatively slow rate such-as 'for example, 5

lcycles per second. For obtaining 'satisfactory indications at 'thisslow sweep, an oscilloscope having a high persistence :screen must befemployed. Such Oscilloscopes require A'high deflect- 'ing voltages, forexample of Iabout 900 'volts R. M. S., orabout 1260 volts frompea'ktopeak.

To obtain 'a circular sweep, 'twovs'inewaves of the samefrequencybut'illlo out of phaseare applied to the vertical andhorizontal deflecting plates of the oscilloscope. While 'satisfactorycircular sweep circuits o'f low voltage havebeenfdisclosed in the priorart such as for example, in A. G. Richardson-TfClark, Serial No.513,198, filed December 6, 1943, and issued December 23, 1948 as PatentNo. 2,457,178'for"Resistance Sine Wave Generator, .it has zbeen-zdifficult to obtain 1 a satisfactory circular sweep circuit Aproducinghigh voltages. y'.fittemptsto amplify-the output of low voltage, lowfrequency sweep circuits have been unsatisfactory since 'the amplifiermust 'be 'a v"D. 1C. amplifier and it isdifiicult to 4obtain -or makeasuitable'D. C. ampliierforsuchuse. A-Besides-such D. C.ampliiierstendto'be cumbersome and expensive.

An object of lthe 'present invention is the'provision of an improvedVsweep circuit for ycathode ray tubes and particularly one whichprovides high sweep voltages of relatively low frequencies.

Other and further objects of the present invention will become apparentand our invention will be best understood from the following descriptionof an embodiment thereof, reference being had to the drawing, in whichthe single ligure is a schematic diagram of a sweep circuit arrangementembodying our invention.

Referring now to the ligure, the sweep circuit includes an oscillator Idesigned to operate at a relatively high frequency, such as, forexample, megacycles, which frequency is higher than the frequency outputof a signal source 2 such as a direction iinding receiver, which latterfrequency may be for example 200i kilocycles and lower. The output ofthe oscillator l is fed to two ampliiiers 3 and 4 respectively. Theseampli fiers are modulated, preferably grid modulated by the output ofsource or receiver 2. This modula- 2 tion is preferably solelya'downward modulation, thatis, the-modulation does not increasethe'outaput of the.ampliiiersbeyondthat producedbythe oscillator but insteaddecreases said output in proportion tothe amount of lthemodulating volt-Aages derived from source 2.

The output of .'ampliiiers 3 and il is fed 'through variable coupling`condensers 5 and i respectively to step-up transformers l and `8respectively. C'ondensers and are used to vary the coupling fbetween'the amplifiers andthe `primary of their respective transformers?and-T8,-so asito vary the "energy impressed upon the primary of each of'said transformers. Condensers l5 and f6 vare zganged itogether and'adapted to 'be :rotated a't'a constant very low frequency 'suchfas'for'exam'pla fcyclesper secondbymeans of amotor 9 or-other suitablemeans `which in turn "is synchronized with #the goniometerof vthedirection finding sysftemforthe switching'offthe directional antennas,yas is 'disclosed in Busignies, Serial No. 553598,f1e'dSeptember lll,1944, for Direction fFinders. Con'densersi and ie are so shapedfthat 4as'they rotate *they vary 'thecoupling -sinusoidally Moreover,:saidcondensers are `ganged together so 'as Ito -lvary Ltheir outputs 90 outof phase with IVeach yother at 'said very low 'frequency 5 cycles :persecond). The secondaries of transformers il and "ii are connected torectiiiers 1D and lAM :which rectify the fC'. -energy supplied thereto,which energy is then passed through filters 'I2 fand F5 3 -respectivelywhich block fout the highest frequency component y(30 megacycl'es')produced lby oscillator i, and Apass the 5 cycle per second component aswell as the components introduced ibyftheumodulation fromirec'eiver 2.The outputs of filters I2 and i3 which are sinusoidal are then passedthrough sets of blocking condensers Ill and l5, respectively to thedeiiecting plates of an oscilloscope i6, the output of iilter l2 beingconnected to the vertically deiiecting plates I1 and the output offilter i3 being connected to the horizontally deilecting plates i8.

While we have described above the principles of our invention inconnection with speciiic apparatus, it is to be clearly understood thatthis description is made only by way of example and not as a limitationon the scope of our invention as defined in the accompanying claims.

We claim:

1. In a high frequency signalling system employing a cathode ray tube,means for generating a high voltage sweep circuit for said tubecomprising an oscillator producing waves of a frequency of the order ofseveral megacycles, a.

further source of signalling frequency of the order of a few hundredkilocycles and lower, means including an amplifier for modulating thefirst mentioned waves by said signalling frequency, capacitive means forcyclically varyingthe output of the amplifier at a relatively lowfrequency, means for increasing the voltage of'said low frequencycomponent, and means for rectifying and filtering said increasedvoltage.

2. System according to claim 1, in which the means for increasing thevoltage comprises aA step-up transformer.

3. System according to claim 1, wherein the output of the modulatingmeans comprises two channels and said capacitive meansis included in therespective channels and adjusts the respective voltages therein to be inphase quadrature, and means for applying the outputs of said channels tothe deilecting circuits of said cathode ray tube.

4. In combination, a source of signal energy having a relatively mediumfrequency, an oscilput of said oscillator and modulated by the energyfrom said source, means for sinusoidally varying the output of each ofsaid amplifiers at a common relatively low frequency but 90 out ofphase, means for removing the high frequency components of thesinusoidally varied output of t each amplifier while passing the mediumand low lator adapted to operate at a frequency of the order of4 severalmegacycles, an ampliiier'connected to the output of said oscillator andmodulated by the energy from said source, a rectifier, variable couplingmeans arranged between the output of said amplifier and said rectifier,said coupling means being adapted to sinusoidally vary the output ofsaid amplifier at a relatively low frequency, a filter connected to theoutput of said rectifier and adapted to block the relatively highfrequency components While passing the medium and lovv'frequency`components, and an oscilloscope having a pair of deflection platescoupled to the output of said filter.

5. In a circuit for producing a circular sweep for a cathode ray tube;an oscillator producing a wave of the order of several megacyclesmodulated by a signal wave of lower frequency, a pair of amplifiers eachcoupled to the output of said oscillator and adapted to amplify itsoutput, capacitive coupling means for cyclically varying the output ofeach of said ampliers at a common low frequency and 90 out of phase, andmeans for removing the high frequency components of the cyclicallyvaried output of each amplifier while passing said low frequencyvariations, said low frequency variationsbeing applied to separate pairsof the deflecting plates of said tube.

6. In a circuit according to claim 5, including a pair of rectiiiers,said capacitive means variably coupling said amplifiers to separate onesof said rectiiiers at a sinusoidally varying low frequency and 90 out ofphase at said low frequency, and

frequency variations, and an oscilloscope having two pairs of deiiectionplates to which the 'energy passed through said last-mentioned means isapplied.

8. An indicator circuit comprising a source of high frequency waves ofthe order of several megacycles, a source of modulation signals, an

amplifier circuit, means for modulating said high frequency Wavescomprising said modulation signals and said amplifier circuit,electrostatic couping means, means for variably controlling the degreeof coupling of said last named means at a given frequency rate, meansfor modulating at said given frequency the modulation output of saidamplifier circuit comprising said electrostatic coupling means, meansincluding a stepup transformer for amplifying said given frequencymodulated signals, means for demodulating said given frequency modulatedfor obtaining a given frequency modulation envelope of said highfrequency waves, means for applying said last named signals to saidindicator.

LOUIS A. DE ROSA.

FRANK J. LUNDBERG.

REFERENCES CITED The following'references arel of record in the ille ofthis patent:

UNITED STATES PA'I'ENTs Number Name Date 2,135,171 Chireix Nov. 1, 19382,215,197 Sherman Sept. 17, 1940 2,241,809 De Forest May 13, 19412,275,974 Mathes Mar. 10, 1942 2,374,666 Cunnii May 1, 1945 2,421,747-Engelhardt June 10, 1947

